
Re: NonEuclidean Arithmetic
Posted:
Sep 10, 2012 2:31 AM


How about actually addressing my rebuttal below to your claim that kids are too stupid to notice and learn, at about age 7 when they learn multiplication and are taught the calculative repeated addition, the differences in the type of motion they see on the number line when they multiply in comparison to when they add, where one type of motion is scaling and proportional and the other one is not?
And if you think that they are not so stupid, then why should they not learn it? You think it would harm their minds or something?
On Mon, Sep 10, 2012 at 12:32 AM, Wayne Bishop <wbishop@calstatela.edu> wrote: > More important than the intelligence of kids is the intelligence, > experience, and intuition of good elementary school teachers. Allah forbid > that they get this kind "help" in their preservice or inservice training or > curricular materials. > > Beyond that, you are way too generous to Keith Devlin. He goes way beyond > the more advanced perspective that they are not one and the same and > pretends that this is some sort of hurdle for students, "telling young > pupils it is inevitably leads to problems when they subsequently learn that > it is not." I defy anybody to find even one such student much less > "invariably". Any of us care to pretend that we were confused at some later > point? We just never could understand Dedekind cut multiplication because > we were so tied to believing his strawman "is"? > http://www.maa.org/devlin/devlin_06_08.html > > Wayne > > At 05:40 PM 9/9/2012, Paul Tanner wrote: > > On Sun, Sep 9, 2012 at 7:46 PM, Wayne Bishop <wbishop@calstatela.edu> wrote: >> At 12:10 PM 9/9/2012, Paul Tanner wrote: >> >> Is the multiplication of two irrationals, especially two nonalgebraic >> irrationals like the product e(pi), a computable procedure? >> >> Computation is fine when you actually do it, but when you can't, you >> will need a definition of multiplication that holds up on all of the >> reals, not just on almost none of them. >> >> >> Forget the "Non" part of the thread title and the Greeks told us how to >> multiply any two (positive) numbers some time ago, no approximations  or >> even convenient notation for approximations  needed. That said, it's no >> way to begin multiplication with little children. Repeated addition is >> the >> way to go even with fractions >> m/n = m(1/n) so that: (k/l)(m/n) = km(1/lm) with the nice picture to go >> with >> it, and is analogous with a nice picture that goes with mn. >> >> The problem with Devlin's strawman "is" was explained by that great >> communicator former Pres. Clinton. >> >> Wayne >> >> >> > > Neither Devlin nor I say what you say we say. I believe that he said > that teaching repeated addition is fine, just not as one and the same > thing as multiplication, since this repeated addition model fails > utterly when confronted with multiplying two irrationals later on. And > it has to be totally defined for two rationals  as I said repeatedly, > with two rationals we can no longer use the two original factors, > where with before rationals, the two original factors are directly > used: ab means a instances of b added together, but with (a/b)(c/d), > we have to abandon both a/b and c/d and derive two new factors to do > this repeated addition thing, one factor being a and the other being > c/(bd). Yes, it;s still socalled "repeated addition" but so what? > There has to be a major redefinition. > > But with scaling, there has to be *no* redefinition even for two > irrationals. > > Kids are smarter than you think. > > As an extra model to go with the repeated addition model, this extra > model being able to hold up totally unchanged even with multiplying > two irrationals: > > Kids are smart enough to see that if we start at point 1 and make that > length 3 times longer we end up at point 3. Nothing wrong with using > repeated addition here as a model to count up to the target point, and > I think Devlin is fine with that. They are smart enough to then see > that if we start at point 5 and make that length of 3 times longer > then we end up at point 15. Again, nothing wrong with using repeated > addition here as a model to > count up to the target point, and I think Devlin is fine with > that. Finally kids are smart enough to see the same pattern being > done: "Stretching a length of 5 out to make it 3 times longer is the > same pattern as "stretching" a length of 1 out to make it 3 times > longer. 15 is to 5 as 3 is to 1. > > If you think 7 year old kids are too stupid for this, then OK, go > ahead and believe it. I don't believe it. You shortchange them, I > think, in terms of what they are capable. > > And I reiterate everything I said in my post > > http://mathforum.org/kb/message.jspa?messageID=7886496 > > in this thread, especially on proportional reasoning.

